1. Technical Field
This invention generally relates to devices for converting hydraulic or pneumatic pressure sources to rotary motion and, in particular, this invention relates to a hydraulic/pneumatic transmission which uses a turbine-type assembly for direction selection and gearing.
2. Background Art
There exist many varied applications in which it is desirable to convert a hydraulic or pneumatic pressure source into rotary energy which can then be utilized to perform a specific task. The use of fluidics in power transfer is becoming more and more popular, due mainly to the simplicity and efficiency which fluidics can supply power for a particular application from a remote power plant.
A typical example of a pneumatic application might be in a mechanics shop which utilizes a centralized compressor to power a plurality of power tools. Hydraulic applications include large power tools, vehicles and hydraulic motors which subsequently power electrical generators, etc.
The purpose of a pneumatic or hydraulic motor is to convert a pressurized fluid source to a mechanical rotary output. Motor rpm is typically controlled with a fluid bypass mechanism which diverts a portion of the pressurized fluid to the return loop of the hydraulic system. This diverted energy is in effect wasted and does not contribute to the available torque or rpm of the mechanical rotation. A mechanical transmission must be used in connection with most hydraulic motors to obtain the maximum energy output at a given rpm.
A partial solution to the problem is offered by Levites, U.S. Pat. No. 4,624,110. Levites teaches a turbine/power transmission which selectively drives one of a plurality of turbine wheels to vary the torque and rpm of the output shaft. The various diameter turbine wheels, or runners, are radially attached to the drive shaft in side-by-side spaced relation. Levites teaches the use of a single pressurized fluid injector whose position can be shifted from turbine to turbine. The pressurized fluid enters each individual turbine wheel at its outside annular edge and is subsequently exhausted through a hollow output shaft. The number of available torque outputs is equal to the number of individual turbine runners. Obviously, the more distinct torque outputs a particular application requires, the larger the actual device becomes. No intermediate "gearing" is possible using the single pressurized fluid injector. Also, the Levites device is not well suited for higher viscosity fluids. Higher viscosity fluids typically require larger volume flow. The exhaust, or scavenge, configuration of Levites is necessarily small since it is disposed within the output shaft. Higher viscosity fluids are also more susceptible to centrifugal effects in the spinning turbine and naturally resist axial scavenging.
What is needed is a device for converting a pressurized fluid source, both hydraulic and pneumatic, to a rotary motion output having a large number of speed/torque settings while still maintaining reduced overall dimensions.
Accordingly, it is an object of the present invention to provide a transmission for converting pressurized hydraulic or pneumatic fluid to a rotational motion with a greater number of possible outputs and which is more compact and efficient than heretofore possible.